Manufacture of sheets or bands from highly viscous cellulose solutions



July 27, 1943. 7

A. WUNDERER mmumc'ruarz OF srmms on BANDS mom HIGHLY VISCOUS CELLULOSESQLUTIONS Filed Aug. 26, 1939 INVENTOR HIS ATTORNEYS the paste can becut with a knife.

PMs-1 21,1943

UNITED smrss PATENT OFFICE MANUFACTURE OF SHEETS OB BANDS VISCOUBOELLULOSE I'BOM HIGHLY SOLUTIONS Anton Wanderer, Wlesbaden-Blebrlch,Germany; yeeted in the Alien Property Custodian Application August 28,1939, Serial No.

In Germany August 29, 1938 lCiairn. (c1. rs-s'l') The present inventionrelates to the production of foils or hands of regenerated cellulosefrom highly viscous spinning masses.

The manufacture of sheets of regenerated cellulose from viscose presentsno difiiculties in respect of the production of a smooth surface, so-

in sulphuric acid, phosphoric acid or zinc chloride solution or othersolvents which dissolve cellulose. Such solutions when they have theconcentration necessary in making sheets and contain, for instance, fiveper cent or more of cellulose have a pasty consistency; the viscosity isso high, especially at low temperatures, that If such a solution isextruded from a spinning slot into a that its usefulness is generallydiminished.

This invention relates to a method by which there may be obtained from ahighly viscous solution of cellulose, for instance a pasty solution ofcellulose in sulphuric acid, phosphoric should not be heated or shouldbe heated to quite,

a low degree, otherwise there will be too much degradation of thespinning mass, whereby the obtained films would lose too many of theirmechanical properties. The interior of the extruded spinning'massremains therefore pasty. This is the meaning of the term heatsuperficially.

It is recommended that a cold spinning mass should be supplied to thespinning slot, 1. e., a spinning mass the temperature of which is belowroom temperature. The temperature should preferably not exceed about 10C.

The heating of the spinning mass at that part which after regenerationof the cellulose becomes the'surface of the foil may be achieved byheating uniformly to the required temperature the two edges or lips ofthe spinning slot. In this manner the outer layers of the spinning massI are warmed to the necessary degree during their acid or the like,sheets, films or bands having smooth surfaces.

The new process is characterized by the fact that the highly viscousspinning mass is heated superficially while it passes through the slotof the employed spinning device, that is to say the part of the spinningmass which is to come into contact with the inner surface of thespinning slot is suitably warmed. In this manner the spinning mass isliquefied at its surface by degradation. The viscosity at the surface ofthe spinning mass can be lowered to a degree at which the issue from thespinning orifice is faultless and the surface of the extruded sheet isquite smooth I passage through the slot. The temperature of the lipsdepends on the temperature of the spinning mass and the period of timeduring which the latter is in contact with the heated parts. In generalthe temperature of the spinning lips should be between 30 and C. Whenthe speed of the spinning is very high, the temperature may also behigher, for instance 200 or 300' C.

The following example illustrates the invention:

A solution of cellulose in sulphuric acid having a temperature betweenabout 0 and 10 C. and containing 7-8 per cent of cellulose, 57-60 percent of sulphuric acid and the rest water is fed under' a pressure ofsome atmospheres to a spinning device such as that indicated by wayof'example in the accompanying drawing which is a transverse sectionthrough the device. The spinning device i has a slot 5, the edges ofwhich are .14 mm. distant from each other. By means of the channels 2adapted for circulation of hot water the temperature of these'lips israised to about 35-40 C. The length of the path along which the spinningsolution 3 flows, namely the heated surfaces 4 of the slot is about 30mm. The speed of discharge of the spinning solution is about 1 m. perminute. If the speed of spinning is increased the temperature of thelips must be correspondingly raised or the heated surface increased sothat the heating of the surface of the spinning solution ismaintained'at .its previous value. When the speed of the spinning isdiminished the conditions are reversed. From the spinning slot thesolution issues into a precipitating bath of the usual composition, for

face.

If the temperature of the spinning lips is too high there is the dangerthat a sheet of poor tensile strength will be produced. When 10 thetemperature is too low on the other hand the surface of the sheet is Iclaim:

liable to be rifled.

' said slot with a precipitating bath.

A process for producing bands of regenerated cellulose with smoothsurfaces which comprises leading to a spinning slot 9. highly viscouspaste of cellulose dissolved in a solvent selected from the classconsisting of sulphuric and phosphoric acids, said paste being at atemperature not exceedinglo" C.,- subjecting the mass adjacent I theslot and onlyat the periphery of the mass to a temperature of from 30 to300 C. to efiect liquefaction of the mass only at the surface thereofand treating the mass passing through ANTON WUND

